In recent years the availability, competitive price, and clean burning characteristics of natural gas have made it an attractive fuel for electric power production. Consequently, utility companies have been increasing the capacity factors on existing gas-fired boilers and are adding gas-firing capability to boilers that were originally designed exclusively for oil or coal. During this same time period, the need to control NOx emissions from existing utility and industrial boilers has increased.
Gaseous fuels are burned in boilers, furnaces, and other enclosed furnace chambers. Typically, burning of the fuel occurs as it is mixed with air at one or more burners (e.g., combustors) located in the walls of the furnace chamber. The design of the burner affects the way in which the air and fuel are mixed, which in turn affects the characteristics of the burning process and combustion by-products. Oxides of nitrogen (NOx) are such by-products, and are regulated air pollutants that must be minimized. Various approaches are commercially applied to reduce NOx emissions, including complete replacement of the burners with low-NOx burners, recycling of flue gas to the burner, or other costly physical or operational changes to the boiler or furnace.
It would be highly desirable to provide a retrofittable gas burning technology that achieves NOx reductions at a fraction of the cost and complexity of new burners, Flue Gas Recirculation fans, and postcombustion processes.